Plants processing foods, pharmaceuticals, biological and technological fluid materials generally require fluid piping systems that must be free from voids and crevices to prevent accumulations of materials, that can readily be taken apart for periodic cleaning and that can withstand the application of CIP (clean in place) solutions and steam cycles used for cleaning. The gasket material used at joints in the piping systems must have appropriate resiliency and resistance against deterioration by the chemical and physical characteristics of the fluids under the conditions of temperature and pressure occurring during sanitization, such as the use of 15 psi saturated steam, hot, de-ionized water or hot WFI (water for injection).
As compared to a general use gasket, the material for a sanitary-pipe gasket to be used in manufacturing medicines, foods, etc. must be more carefully selected. This requirement is made to prevent contamination of products by components of the gasket material eluting into the fluid transported through the piping. Accordingly, many sanitary-pipe gaskets have conventionally been formed of silicone rubber which has excellent heat resistance and chemical resistance. Other materials employed in food and pharmacological processing include ethylene propylene diene monomer (EPDM), buna rubber, and fluoroelastomers such as Viton® or FKM 615A™. A dipolymer of vinylidene fluoride and hexafluoroproplyene often used as base elastomers for seals, spacers and gaskets employed in sanitary piping systems.
A pair of known pipe ends equipped with sanitary pipe flange fittings 1, 2 is shown in FIG. 1. Sanitary pipe fittings 1, 2 have flanges 3, 4 with substantially flat facing faces 5, 6 each of which has a recess or annular groove 9, 10 that is designed to accommodate sealing gasket. Typically, a simple O-ring gasket (not shown) or preferably, an O-ring 12, FIGS. 2, 3, fitted with peripheral flat, compressible sections 12a, 12b of elastomeric material, such as shown in U.S. Pat. No. 6,318,576 which is herein incorporated by reference, may be used. Let it be assumed that the original thickness of portions 12a, 12b is “T”.
The pipe fittings are made-up by tightening the screw (not shown) of a conventional hinged clamp (not shown, but see U.S. Pat. No. 4,568,115 which is herein incorporated by reference). The hinged clamp exerts a camming action on the exterior beveled shoulders 7, 8 of flanges 3, 4 forcing flat faces 5, 6 against each other and compressing the gasket 12 (FIG. 2) between them.
Unfortunately, as shown in FIG. 4, if the clamp is tightened too much in an effort to prevent leakage at the joint, the gasket 12 will be unduly compressed causing a portion 12c of gasket 12 to be extruded into the interior lumen ID at the joint between pipes 1, 2. Empirical data tends to show that with an elastomeric gasket typically having a Shore A hardness of 70° a minimum contact pressure of 1.5 N/mm2 is required. This contact pressure corresponds to an elastomeric gasket being compressed by 15 percent of its original thickness.
When a gasket is fabricated of elastomeric material, compressing one dimension of the gasket results in expansion of its other dimension, but the total volume of gasket material remains constant. For example, a 20% axial compression of the gasket thickness will cause a radial elongation of about 25%. Depending on the dimensions of the pipe flanges and that of the gasket, the radial elongation of the gasket 12 may cause portion 12c to be extruded into the pipe lumen. Projecting portion 12c can then be abraded by the flow of material being carried through the sanitary pipes.
This is shown in FIG. 4 where a conventional gasket 12 made of elastomeric material has a pre-compression axial thickness T. When the usual clamp (not shown) is made up to draw the pipe sections axially together gasket 12 is compressed by an amount t so that its final thickness is T−t. At the same time its radial dimension increases. Depending on the amount of compression, the amount of radial increase may cause a portion 12c of the gasket to be extruded into the lumen of the pipe. It is this portion 12c of the gasket that is exposed to the process stream being carried by the pipes.
To comply with sanitary requirements, sanitary piping systems are periodically subjected to high temperature steam sterilization. Under such conditions, gaskets tend to deteriorate. The deterioration leads to a lowering of elasticity, the gasket becomes stiff and cracks form. When the piping system is then used to carry a process stream a portion of the gasket surface 12c may erode so that some small particles thereof become detached and enter and contaminate the process stream.
While modern elastomeric materials are designed to resist deterioration under operating conditions, there needs to be some way of telling when a gasket has in fact deteriorated to the point where it contaminates the process stream. Unfortunately, the detection of miniscule portions of elastomeric material in the process stream has required exotic spectrographic equipment.
While systems have been employed were feromagnetic additives have been incorporated into the elastomeric compositions to allow for detection of particulates lost from gaskets or o-rings. Such additives, however, are not distinguishable from their surroundings if present in an environment which shields magnetometers or which would produce sufficient false positives to render such detection methods inoperable.
What is needed therefore is a method for improving the detection of fragmented sanitary seals and gaskets in applications where detection use of magnetometers are unsuitable.